Self-attaching nut and method of making same

Abstract

A method of making a self-attaching nut or pierce nut, such as a round nut having cylindrical pilot, an annular groove surrounding the pilot and a panel supporting flange portion surrounding the groove, wherein the groove bottom wall includes a plurality of circumferentially spaced anti-rotation protuberances separated by radial channels and wherein the flange portion is preferably tapered toward the pilot portion to provide a re-entrant groove which provides a secure installation to a panel. The method includes first forming a nut blank having the general configuration of the nut with a continuous annular protuberance and an annular flange portion which extends perpendicular to the groove bottom wall. A forming punch having a cylindrical axial bore and a plurality of generally rectangular or trapezoidal circumferentially spaced projections on the punch forming end is then driven into the groove to telescopically receive the pilot portion and driven against the continuous annular protuberance to form a plurality of circumferentially spaced protuberances which extend from the pilot portion to a midportion of the groove bottom wall. In the most preferred embodiment, the projections on the punch are spaced from the bore, such that semi-circular bridging portions are formed integral with the pilot portion and adjacent protuberances.